Generally speaking vehicle for vehicle belt drives are quieter, stronger and lighter (read less unsprung weight) whilst having longer service life than chains and of course require minimal maintenance. They do have to be tensioned accurately though (which reduces snatch) and may not be suitable for applications where the swing arm pivot is not concentric with drive sprocket, causing drive length variations during suspension articulation. As for power loss, its minimal - one back to back test on a motorbike showed a one hp improvement over the OE chain.
